Germ cell arrest associated with aSETX mutation in ataxia oculomotor apraxia type 2.

Ataxia with oculomotor apraxia type 2 (AOA2) is a rare autosomal recessive neurodegenerative disorder characterized by cerebellar atrophy, peripheral neuropathy and oculomotor apraxia. It is caused by mutations in the SETX gene that encodes senataxin, a ubiquitously expressed protein that mediates processes, including transcription, transcription termination, DNA repair, RNA processing, DNA-RNA hybrid (R-loop) elimination and telomere stability. In mice, senataxin is essential for male germ cell development and fertility through its role in meiotic recombination and sex chromosome inactivation. AOA2 is associated with hypogonadism in women, but there are no reports of hypogonadism or infertility in men. We describe the first case of human male infertility caused by germ cell arrest in a man with AOA2. Our patient has a homozygous mutation in the SETX gene (NC_000009.11:g.135158775dup), which results in a frameshift and premature protein termination (NM_015046.6:c.6422dup, p.[Ser2142Glufs*23]). In accordance with the murine phenotype, testis histology revealed disrupted seminiferous tubules with spermatogonia and primary spermatocytes, but absent spermatids. Collectively, these data support an essential role of senataxin in human spermatogenesis, and provide a compelling case that men with AOA2 should be counselled at diagnosis about the possibility of infertility.

A longitudinal study of the SF-36 version 2 in Friedreich ataxia.

OBJECTIVES: The Medical Outcomes Study 36 item Short-Form Health Survey (SF-36) is one of the most commonly used patient reported outcome measure. This study aimed to examine the relationship between SF-36 version 2 (SF-36V2) summary scores and Friedreich ataxia (FRDA) clinical characteristics, and to investigate the responsiveness of the scale, in comparison with the Friedreich Ataxia Rating Scale (FARS), over 1, 2 and 3 years. MATERIALS AND METHODS: Descriptive statistics were used to examine the characteristics of the cohort at baseline and years 1, 2 and 3. Correlations between FRDA clinical characteristics and SF-36V2 summary scores were reported. Responsiveness was measured using paired t tests. RESULTS: We found significant correlations between the physical component summary (PCS) of the SF-36V2 and various FRDA clinical parameters but none for the mental component summary. No significant changes in the SF-36V2 were seen over 1 or 2 years; however, PCS scores at Year 3 were significantly lower than at baseline (-3.3, SD [7.6], P=.01). FARS scores were found to be significantly greater at Years 1, 2 and 3 when compared to baseline. CONCLUSIONS: Our findings suggest that despite physical decline, individuals with FRDA have relatively stable mental well-being. This study demonstrates that the SF-36V2 is unlikely to be a useful tool for identifying clinical change in FRDA therapeutic trials.

A Novel Mechanism for Human Cardiac Ankyrin-B Syndrome due to Reciprocal Chromosomal Translocation.

BACKGROUND: Cardiac rhythm abnormalities are a leading cause of morbidity and mortality in developed countries. Loss-of-function variants in the ANK2 gene can cause a variety of cardiac rhythm abnormalities including sinus node dysfunction, atrial fibrillation and ventricular arrhythmias (called the "ankyrin-B syndrome"). ANK2 encodes ankyrin-B, a molecule critical for the membrane targeting of key cardiac ion channels, transporters, and signalling proteins. METHODS AND RESULTS: Here, we describe a family with a reciprocal chromosomal translocation between chromosomes 4q25 and 9q26 that transects the ANK2 gene on chromosome 4 resulting in loss-of-function of ankyrin-B. Select family members with ankyrin-B haploinsufficiency due to the translocation displayed clinical features of ankyrin-B syndrome. Furthermore, evaluation of primary lymphoblasts from a carrier of the translocation showed altered levels of ankyrin-B as well as a reduced expression of downstream ankyrin-binding partners. CONCLUSIONS: Thus, our data conclude that, similar to previously described ANK2 loss-of-function "point mutations", large chromosomal translocations resulting in ANK2 haploinsufficiency are sufficient to cause the human cardiac ankyrin-B syndrome. The unexpected ascertainment of ANK2 dysfunction via the discovery of a chromosomal translocation in this family, the determination of the familial phenotype, as well as the complexities in formulating screening and treatment strategies are discussed.

To tell or not to tell - what to do about p.C282Y heterozygotes identified by HFE screening.

Hereditary hemochromatosis (HH) is a common preventable disorder of iron overload that can result in liver cirrhosis and reduced lifespan. Most HH is due to homozygosity for the HFE p.C282Y substitution. We conducted a study of screening for p.C282Y in high schools where p.C282Y heterozygotes (CY) individuals were informed of their genotype by letter. We studied whether these individuals understood the implications of their genotype, whether this resulted in anxiety or reduced health perception and whether cascade testing was higher in families of CY than wild-type homozygous (CC) individuals. We found 586 of 5757 (1 in 10) screened individuals were CY. One month after receiving their result, 83% correctly answered that they have one copy of p.C282Y. There was no adverse change in anxiety or health perception from prior to screening to 1 month after receiving results. Significantly more family members of CY individuals than CC individuals were informed about HH and had testing for HH. In conclusion, we found that informing CY individuals of their genotype does not increase anxiety and the implications are generally well understood. This leads to cascade testing in a minority of families. CY individuals should be informed of their genetic status when identified by population screening.

Decreased functional brain activation in Friedreich ataxia using the Simon effect task.

The present study applied the Simon effect task to examine the pattern of functional brain reorganization in individuals with Friedreich ataxia (FRDA), using functional magnetic resonance imaging (fMRI). Thirteen individuals with FRDA and 14 age and sex matched controls participated, and were required to respond to either congruent or incongruent arrow stimuli, presented either to the left or right of a screen, via laterally-located button press responses. Although the Simon effect (incongruent minus congruent stimuli) showed common regions of activation in both groups, including the superior and middle prefrontal cortices, insulae, superior and inferior parietal lobules (LPs, LPi), occipital cortex and cerebellum, there was reduced functional activation across a range of brain regions (cortical, subcortical and cerebellar) in individuals with FRDA. The greater Simon effect behaviourally in individuals with FRDA, compared with controls, together with concomitant reductions in functional brain activation and reduced functional connectivity between cortical and sub-cortical regions, implies a likely disruption of cortico-cerebellar loops and ineffective engagement of cognitive/attention regions required for response suppression.

Unclassified white matter disorders: A diagnostic journey requiring close collaboration between clinical and laboratory services.

BACKGROUND: Next generation sequencing studies have revealed an ever-increasing number of causes for genetic disorders of central nervous system white matter. A substantial number of disorders are identifiable from their specific pattern of biochemical and/or imaging findings for which single gene testing may be indicated. Beyond this group, the causes of genetic white matter disorders are unclear and a broader approach to genomic testing is recommended. AIM: This study aimed to identify the genetic causes for a group of individuals with unclassified white matter disorders with suspected genetic aetiology and highlight the investigations required when the initial testing is non-diagnostic. METHODS: Twenty-six individuals from 22 families with unclassified white matter disorders underwent deep phenotyping and genome sequencing performed on trio, or larger, family groups. Functional studies and transcriptomics were used to resolve variants of uncertain significance with potential clinical relevance. RESULTS: Causative or candidate variants were identified in 15/22 (68.2%) families. Six of the 15 implicated genes had been previously associated with white matter disease (COL4A1, NDUFV1, SLC17A5, TUBB4A, BOLA3, DARS2). Patients with variants in the latter two presented with an atypical phenotype. The other nine genes had not been specifically associated with white matter disease at the time of diagnosis and included genes associated with monogenic syndromes, developmental disorders, and developmental and epileptic encephalopathies (STAG2, LSS, FIG4, GLS, PMPCA, SPTBN1, AGO2, SCN2A, SCN8A). Consequently, only 46% of the diagnoses would have been made via a current leukodystrophy gene panel test. DISCUSSION: These results confirm the importance of broad genomic testing for patients with white matter disorders. The high diagnostic yield reflects the integration of deep phenotyping, whole genome sequencing, trio analysis, functional studies, and transcriptomic analyses. CONCLUSIONS: Genetic white matter disorders are genetically and phenotypically heterogeneous. Deep phenotyping together with a range of genomic technologies underpin the identification of causes of unclassified white matter disease. A molecular diagnosis is essential for prognostication, appropriate management, and accurate reproductive counseling.

Impaired inhibition of prepotent motor tendencies in Friedreich ataxia demonstrated by the Simon interference task.

Friedreich ataxia (FRDA) is the most common of the genetically inherited ataxias. We recently demonstrated that people with FRDA have impairment in motor planning - most likely because of pathology affecting the cerebral cortex and/or cerebello-cortical projections. We used the Simon interference task to examine how effective 13 individuals with FRDA were at inhibiting inappropriate automatic responses associated with stimulus-response incompatibility in comparison with control participants. Participants had to respond to arrow targets according to two features which were either congruent or incongruent. We found that individuals with FRDA were differentially affected in reaction time to incongruent, compared with congruent stimuli, when compared with control participants. There was a significant negative correlation between age of onset and the incongruency effect, suggesting an impact of FRDA on the developmental unfolding of motor cognition, independent of the effect of disease duration. Future neuroimaging studies will be required to establish whether this dysfunction is due to cerebellar impairment disrupting cerebro-ponto-cerebello-thalamo-cerebral loops (and thus cortical function), direct primary cortical pathology, or a possible combination of the two.

SMARCB1/INI1 maternal germ line mosaicism in schwannomatosis.

Schwannomatosis is characterized by the development of multiple schwannomas of the nervous system, but without the occurrence of vestibular schwannomas. Most cases of schwannomatosis are thought to be sporadic, representing the first case in a family due to a new mutation in the causative gene. We recently identified SMARCB1/INI1 as a schwannomatosis-predisposing gene. Here, we analyzed this gene in a schwannomatosis family with two affected children, but with clinically unaffected parents. Both affected individuals carried a constitutional SMARCB1 mutation, c.1118+ 1G>A, that changes the donor splice site sequence of intron 8, causing skipping of exon 8 and resulting in the in-frame deletion of 132 nucleotides in the transcript. The mutation was not evident in constitutional DNA of the parents. Haplotyping revealed that the chromosome 22 segment that carries the mutant SMARCB1 allele originated from the mother. She transferred the same chromosome 22 segment, however, with a wild-type SMARCB1 copy, to a third unaffected child. Our findings indicate that the mother is germ line mosaic for the SMARCB1 mutation. In conclusion, our study shows for the first time that germ line mosaicism may occur in schwannomatosis, which has implications for genetic counseling in this disease.

Evaluation of a multi-disease carrier screening programme in Ashkenazi Jewish high schools.

A screening programme for Tay Sachs disease (TSD) carrier status was introduced in high schools in Victoria, Australia in 1997, and was expanded to screen for six other genetic conditions common in the Ashkenazi Jewish population in 2008. The aim of this study was to evaluate the current programme and compare it with an evaluation of the programme when screening was offered for TSD alone. All students from Jewish high schools in Melbourne who offered the programme in 2009 were invited to participate in the study. A purpose-designed questionnaire explored the following domains: knowledge (disease and genetics), reasons for screening, anxiety, and predicted negative feelings if found to be a carrier. Two hundred and seventy-three students were offered screening, and 272 (99.6%) completed the questionnaire. Only two students chose not to have screening. Two hundred and seventy-one students were in the penultimate year of high school (99.6%) and 222 were of Ashkenazi Jewish descent (82.5%). The main reasons for choosing screening were the desire to know carrier status and convenience. Knowledge level decreased and negative feelings increased in the current cohort compared to that when screening was offered for TSD alone. We conclude that the current programme is efficient, although increasing the number of conditions resulted in a decrease in knowledge and increase in predicted negative feelings if found to be a carrier of one of the conditions. This has implications for multi-disease screening programmes that will increase in frequency as more conditions can be screened for and costs diminish.

Implementation of ironXS: a study of the acceptability and feasibility of genetic screening for hereditary hemochromatosis in high schools.

Hereditary hemochromatosis (HH), most often due to HFE C282Y homozygosity, is an iron overload disorder that can result in severe morbidity including hepatic cirrhosis. Predisposition to HH is easily diagnosed and morbidity is preventable by maintaining normal body iron and thus calls have been made to introduce community screening. The current study has been designed to assess the acceptability and feasibility of HH screening in high schools. Students (mostly 15-16 years of age) watched a purpose-designed DVD for education about HH. Those with parental consent were then offered cheek-brush screening for C282Y. Students completed a questionnaire prior to screening. The program was offered to 9187 students at 32 schools and 3489 (38%) had screening. Nineteen C282Y homozygotes (1 in 183) and 376 heterozygotes (1 in 9.3) were identified. More than 90% of students answered each of five knowledge questions correctly. Eight homozygotes (42%) had elevated transferrin saturation, but only two (10.5%) had marginally elevated serum ferritin (SF). We have shown that genetic screening for HH can successfully be offered in the high school setting. Ongoing research in this study will answer questions about the impact of high school students learning that they are at risk of HH.

Genetic selection for deafness: the views of hearing children of deaf adults.

The concept of selecting for a disability, and deafness in particular, has triggered a controversial and sometimes acrimonious debate between key stakeholders. Previous studies have concentrated on the views of the deaf and hard of hearing, health professionals and ethicists towards reproductive selection for deafness. This study, however, is the first of its kind examining the views of hearing children of deaf adults towards preimplantation genetic diagnosis and prenatal diagnosis to select for or against deafness. Hearing children of deaf adults (or CODAs, as they call themselves, and are widely known in the deaf community) straddle both the deaf and hearing worlds, and this dual perspective makes them ideally placed to add to the academic discourse concerning the use of genetic selection for or against deafness. The study incorporated two complementary stages, using initial, semistructured interviews with key informants (CODAs and health professionals) as a means to guide the subsequent development of an electronic survey, completed anonymously by 66 individuals. The participants shared many of the same views as deaf individuals in the D/deaf (or "culturally deaf") community. The similarities extended to their opinions regarding deafness not being a disability (45.5% believed deafness was a distinct culture rather than a disability), their ambivalence towards having hearing or deaf children (72.3% indicated no preference) and their general disapproval of the use of genetic technologies to select either for or against deafness (60% believed that reproductive technologies, when used to select for or against deafness, should not be available to the community).

Variants in ACTG2 underlie a substantial number of Australasian patients with primary chronic intestinal pseudo-obstruction.

BACKGROUND: Primary chronic intestinal pseudo-obstruction (CIPO) is a rare, potentially life-threatening disorder characterized by severely impaired gastrointestinal motility. The objective of this study was to examine the contribution of ACTG2, LMOD1, MYH11, and MYLK mutations in an Australasian cohort of patients with a diagnosis of primary CIPO associated with visceral myopathy. METHODS: Pediatric and adult patients with primary CIPO and suspected visceral myopathy were recruited from across Australia and New Zealand. Sanger sequencing of the genes encoding enteric gamma-actin (ACTG2) and smooth muscle leiomodin (LMOD1) was performed on DNA from patients, and their relatives, where available. MYH11 and MYLK were screened by next-generation sequencing. KEY RESULTS: We identified heterozygous missense variants in ACTG2 in 7 of 17 families (~41%) diagnosed with CIPO and its associated conditions. We also identified a previously unpublished missense mutation (c.443C>T, p.Arg148Leu) in one family. One case presented with megacystis-microcolon-intestinal hypoperistalsis syndrome in utero with subsequent termination of pregnancy at 28 weeks' gestation. All of the substitutions identified occurred at arginine residues. No likely pathogenic variants in LMOD1, MYH11, or MYLK were identified within our cohort. CONCLUSIONS AND INFERENCES: ACTG2 mutations represent a significant underlying cause of primary CIPO with visceral myopathy and associated phenotypes in Australasian patients. Thus, ACTG2 sequencing should be considered in cases presenting with hypoperistalsis phenotypes with suspected visceral myopathy. It is likely that variants in other genes encoding enteric smooth muscle contractile proteins will contribute further to the genetic heterogeneity of hypoperistalsis phenotypes.

How is disease progress in Friedreich's ataxia best measured? A study of four rating scales.

BACKGROUND: Friedreich's ataxia (FRDA), the most common genetic cause of ataxia, is characterised by progressive neurodegeneration and cardiomyopathy. Initial treatments are likely to slow progression rather than reverse morbidity. An appropriate and sensitive scale to measure disease progress is critical to detect the benefit of treatments. OBJECTIVE: To compare the Friedreich Ataxia Rating Scale (FARS) with other scales proposed as outcome measures for FRDA. METHODS: 76 participants were assessed with the FARS and the International Cooperative Ataxia Rating Scale (ICARS) and 72 of these participants were also assessed with the Functional Independence Measure and the Modified Barthel Index. 43 participants had repeat measures at an interval of 12 months. Sensitivity and responsiveness were assessed using the effect size for each measure and the sample size required for a placebo-controlled clinical trial. RESULTS: The FARS showed a high correlation with the other three measures. A significant change in the score over 12 months was detected by the FARS, the International Cooperative Ataxia Rating Scale and the Functional Independence Measure. The FARS had the greatest effect size and requires fewer patients for an equivalently powered study. CONCLUSIONS: Of the scales assessed, the FARS is the best to use in clinical trials of FRDA. This is based on effect size, and power calculations that show that fewer participants are required to demonstrate the same effect of an intervention. Further work is required to develop more sensitive and responsive instruments.

Quality of life in Friedreich ataxia: what clinical, social and demographic factors are important?

The aim of this study was to examine the impact of Friedreich ataxia (FRDA) on quality of life (QOL) using a generic tool to explore factors potentially associated with health status. Sixty-three individuals with genetically confirmed FRDA, self completed the Medical Outcomes Study 36 item Short Form Health Survey Version 2 (SF-36V2) and were assessed using the FRDA Rating Scale. Disease-specific, demographic, and social characteristics were also recorded. SF-36V2 results were compared with Australian population norms. Sample subgroups of disease severity and age at disease onset were reviewed. Physical and mental component summaries were examined in relation to clinical and social characteristics using multiple linear regression. QOL is significantly worse in individuals with FRDA compared with population norms. Those with severe disease did not perceive a lower QOL than those with mild or moderate disease except in their physical functioning. A later age of onset and increased disease severity were negatively associated with physical QOL, whilst, increased disease duration was positively associated with mental QOL. There were limitations associated with the use of SF-36V2 in the FRDA population. Further exploration of health-related QOL and FRDA may benefit from the use of a more appropriate generic tool.

Use of community genetic screening to prevent HFE-associated hereditary haemochromatosis.

HFE-associated hereditary haemochromatosis is a recessive, iron-overload disorder that affects about one in 200 north Europeans and that can be easily prevented. However, genetic screening for this disease is controversial, and so we assessed whether such screening was suitable for communities. Cheek-brush screening for the Cys282Tyr HFE mutation was offered to individuals in the workplace. Outcomes were assessed by questionnaires before and after testing. 11,307 individuals were screened. We recorded no increase in anxiety in individuals who were homozygous for the Cys282Tyr mutation or non-homozygous. Self-reported tiredness before testing was significantly higher in homozygous participants than in non-homozygous participants (chi2 test, p=0.029). Of the 47 homozygous individuals identified, 46 have taken steps to treat or prevent iron accumulation. Population genetic screening for HFE-associated hereditary haemochromatosis can be practicable and acceptable.

Persistent truncus arteriosus in monozygotic twins: case report and literature review.

We report on a pair of monozygotic twins with persistent truncus arteriosus. They had no evident clinical signs of DiGeorge syndrome. Pathologic examination of the placenta and DNA analysis in chromosomes 7, 8, and 15 was consistent with monozygosity. Fluorescence in situ hybridization test was negative for chromosome 22q11 microdeletion. Family history revealed a female cousin with tetralogy of Fallot. The isolated presence of this conotruncal abnormality in monozygotic twins is extremely rare. The genetic considerations are discussed.

New variant of familial cerebellar ataxia with hypergonadotropic hypogonadism and sensorineural deafness.

Cerebellar ataxia and hypergonadotropic hypogonadism comprise a rare and presumably heterogeneous association. Inheritance in most cases appears to be autosomal recessive, and associated features include deafness, intellectual impairment, and neuropathy. Typically, onset of ataxia is in the first decade and hypogonadism results in primary amenorrhoea in females. We describe two sisters with a previously undescribed pattern of adult onset progressive cerebellar ataxia and secondary amenorrhoea due to hypergonadotropic hypogonadism. Sensorineural deafness with vestibular hypofunction and peripheral sensory impairment were also present, and intellect was normal. Onset of neurological symptoms was in the third decade, with secondary amenorrhoea occurring at the ages of 16 and 32 years, respectively. The association of ataxia and hypergonadotropic hypergonadism has been classified both as a variant of Holmes type ataxia and as a variant of Perrault syndrome, but we suggest the use of a separate category of ataxia with hypergonadotropic hypogonadism.

Clinical and genetic study of Friedreich ataxia in an Australian population.

Friedreich ataxia is an autosomal recessive disorder caused by mutations in the FRDA gene that encodes a 210-amino acid protein called frataxin. An expansion of a GAA trinucleotide repeat in intron 1 of the gene is present in more than 95% of mutant alleles. Of the 83 people we studied who have mutations in FRDA, 78 are homozygous for an expanded GAA repeat; the other five patients have an expansion in one allele and a point mutation in the other. Here we present a detailed clinical and genetic study of a subset of 51 patients homozygous for an expansion of the GAA repeat. We found a correlation between the size of the smaller of the two expanded alleles and age at onset, age into wheelchair, scoliosis, impaired vibration sense, and the presence of foot deformity. There was no significant correlation between the size of the smaller allele and cardiomyopathy, diabetes mellitus, loss of proprioception, or bladder symptoms. The larger allele size correlated with bladder symptoms and the presence of foot deformity. The duration of disease is correlated with wheelchair use and the presence of diabetes, scoliosis, bladder symptoms and impaired proprioception, and vibration sense but no other complications studied.

Genetic factors in athetoid cerebral palsy.

Within the cerebral palsy syndromes, athetosis is most commonly causally associated with serious perinatal complications. Genetic factors are thought to play a lesser role, although the risk of recurrence in siblings has been suggested to be as high as 10%. We have conducted a clinical study of 22 subjects with a diagnosis of athetoid cerebral palsy and a review of the literature aiming to identify instances of familial recurrence of athetoid cerebral palsy. The birth history, family history, and previous investigations of subjects with athetoid cerebral palsy were studied and subjects were clinically examined for evidence of an underlying genetic etiology. Factors suggesting a genetic cause were specifically sought, such as advanced paternal age, progression of symptoms, and associated congenital abnormalities. No subjects in the study group had similarly affected relatives, and additional features suggesting a genetic cause were not observed. A literature search identified 16 instances of familial recurrence of athetoid cerebral palsy. Familial cases were typically associated with significant spasticity, microcephaly, intellectual disability, seizures, and a lack of history of birth asphyxia, and most could be explained by either autosomal-recessive or X-linked-recessive inheritance. The genetic contribution to athetoid cerebral palsy is small, with an overall risk of recurrence in siblings of about 1%. This risk is lower than previously suggested in the literature.